Celiac disease (CD) is a disease characterised by intolerance to the gluten prolamines of wheat, barley, rye and oats that causes intestinal alterations leading to malabsorption.
Gluten is a complex mixture of proteins and, although the toxic component or components responsible for CD are unknown, the temporary solution consists in eliminating all the gluten components from diets of these patients. In fact, the only truly effective treatment of celiac disease is to follow a strict gluten-free diet. It is, therefore, essential to be able to precisely quantify the amount of gluten in food items to be taken by celiac patients.
However, a reliable method to measure the gluten content of food items has been notably lacking over the last few years. At present, gluten is measured by epitope-dependent methods, such as ELISA, which use monoclonal or polyclonal antibodies. A useful ELISA technique to quantify the gluten contents of food products is described in Sorell et al., in the article titled “An innovative sandwich ELISA system based on an antibody cocktail for gluten analysis” published in FEBS letters, 439, 46-50 (1988).
The routine protocol for gluten analysis in food products, both for heat-treated and non heat-treated items, consists in extracting gluten with a 60% aqueous solution of ethanol (60% ethanol/water) followed by quantification by ELISA.
One of the main problems related with gluten analysis in food products lies in the fact that a large proportion of food products for celiac patients are processed at high temperatures (150-220° C.). Owing to this thermal treatment, most toxic glucose fractions (α-, β-, and γ-gliadines) are denatured and made insoluble and can, therefore, not be extracted using 60% ethanol/water.
Consequently, the gluten measurement of these heat processed food products, regardless of the ELISA test used, is not reliable.